Japanese Patent Publication (Kokai) No. 279445/1993 describes that a film-form molded product, a fiber or the like of a polycaprolactone composition containing a small amount of urethane bonds can be produced by melt blending a polyvalent isocyanate of 0.1 to 5% parts by weight to a polycaprolactone of 100 parts by weight.
Japanese Patent Publication (Kokai) No. 279445/1993 describes that since the presence of gel may cause problems such as fish eye, filament break, or reduction of moldability due to plugging by gel in the nozzle, the amount of polyisocyanate added must be less than 5 parts by weight to a polycaprolactone of 100 parts by weight. Such publicly-known conventional techniques have failed to offer molded products in which polylactone is crosslinked or cured, but considered only partial improvement, for instance, improvement of melt tensile strength by reacting the terminated-hydroxyl group of polylactone with a small amount of isocyanate. Accordingly, a polylactone with rubber elasticity in softened state by heating or shape memorizable property on a satisfactory level has not been obtained, and naturally application development requiring such new functions has not been made yet.